Syntrophomonas erecta sp. nov., a novel anaerobe that syntrophically degrades short-chain fatty acids.

Two novel anaerobes, strains GB4-38(T) and SB9-1, were isolated from an upflow anaerobic sludge blanket reactor for treating bean-curd farm wastewater and lotus field mud, respectively. The strains degraded straight-chain fatty acids with 4-8 carbon atoms in syntrophic association with methanogens and converted 1 mol butyrate into about 2 mol acetate and presumably 2 mol H(2). None of the branched-chain fatty acids tested could be degraded. Benzoate was not degraded. Fumarate, sulfate, thiosulfate, sulfur and nitrate did not serve as electron acceptors for butyrate degradation. In the absence of a methanogen partner, strain GB4-38(T) grew on crotonate in pure culture; the generation time was about 5 h at 37 degrees C. However, strain SB9-1 grew on butyrate plus pentenoate, but not crotonate, in pure culture and the generation time was 18 h at 37 degrees C. Cells of GB4-38(T) and SB9-1 were straight rods and stained Gram-negative. The major cellular fatty acids of GB4-38(T) were C(14 : 0) (29.74 %), C(16 : 0) (17.00 %), C(16 : 1)omega5c (16.63 %) and isoC(17 : 1) I (15.34 %). ll-Diaminopimelic acid existed in the cellular peptidoglycan. The genomic DNA G+C content of strain GB4-38(T) was 43.2 mol%. Phylogenetic analysis based on 16S rRNA gene sequences supported clustering of the two strains with syntrophic bacterial species of the genus Syntrophomonas (89.6-92.4 % sequence similarity), but phenotypic, chemotaxonomic and genetic characters differentiated the two strains from members of this genus. Therefore, it is proposed that the two strains are representatives of a novel species, Syntrophomonas erecta sp. nov. The type strain is GB4-38(T) (=CGMCC 1.5013(T)=DSM 16215(T)).